Delesseria
decipiens Ecology

Distribution Delesseria
decipiens lives in low intertidal to subtidal areas on the west
coast of North America, from Alaska to San Luis Obispo, CA. D.
decipiens is saxicolus,
meaning that it grows on rocks and can be found on the vertical faces
of rocks in the low intertidal areas. D.
decipiens was first collected in 1859 in the Straits de Juan de
Fuca, near present day Washington State. Samples of D. decipiens were
found in the Hopkins Marine Life Refuge growing on buoy lines in late January
and early March. Data collected from the Gilbert M. Smith Herbarium
also indicates that D. decipiens grows in
a wide variety of locations around the Monterey and Carmel Bay areas.
Locations of D. decipiens in the past have included, from north
to south, Point Pinos, Moss Beach, Asilomar, Spanish Bay, Point Joe,
Cypress Point, Pescadero Point, Pebble Beach, Stillwater Cove, Carmel
Beach, Mission Point and Soberanes Point. Herbarium notes suggest that D.
decipiens can grow in a tidal range form 0.5 to -1.5 feet, although
some sources indicate that it grows at depths of 20 feet. Map
of coastline of the Monterey Peninsula.
from Abbott and Hollenberg. Marine Algae of California. Stanford University
Press, Stanford: 1976

Seasonal GrowthDelesseria
decipiens is a spring annual that can be found in the Monterey
Bay region from late January to July. Based on a survey of D. decipiens samples
in the Gilbert M. Smith Herbarium, plants seem to reach their maximum
size, as measured by the length of their primary midrib, in May and
June. There did not appear to be any pattern of reproductive development
with samples becoming reproductively identifiable in April and continuing
through July.
While the seasonal growth patterns in D. decipiens has
not been studied in depth, similar studies have been made on the seasonal growth
patterns of Delesseria sanguinea, a sub-littoral alga that inhabits
European coasts in the North Atlantic. While D. sanguinea is closely
related to D. decipiens, it is an annual plant, not a perennial plant
like D. decipiens so the growth patterns of the two cannot be directly
correlated. D. sanguinea does exhibit similar spring growth patterns,
however, making it a valuable comparison. D. sanguinea shows growth
of new blades beginning in the winter and continuing through the spring and early
summer. Blade initiation is induced by water temperatures bellow 13° C, and
optimal growing temperatures are between 10 and 20°C. Blade degradation begins
in the summer and continues through the fall. Reproduction is under photoperiodic
control, with the algae needing short days of less than 13 hours in order to
stimulate development of reproductive structures. This ensures that the gametophytes
develop simultaneously allowing successful fertilization to occur more often.
Reproduction occurs in the late fall. While D. sanguinea has some major
differences in its seasonal life history, a comparison between the two algae
is valuable in providing information about general characteristics of the genus
and suggesting possible areas of research when studying D. decipiens.

Sensing UV Light Studies
done in Delesseria sanguinea have shown that D.
sanguinea is
a sensitive and reliable indicator of UVB light, demonstrating a significant
reduction in growth rates when compared to exposure to visible sunlight
and UVA light alone. This is significant as continued thinning of the
ozone layer allows more UVB light to reach the earths surface. UVB
is a highly destructive form of UV light and accurate indicators such
as D. sanguinea could
be highly valuable in monitoring the effects of UVB levels on biological
life. It is not currently know whether D. decipiens shares the
same UVB sensitive properties, but testing this property could be an area
of further research.

Delesseria
decipiens as a habitatDelesseria
decipiens can act as a habitat for other invertebrates and marine
organisms. In a sample collected on March 4, 2004 from a buoy line
several invertebrates were found in association with D. decipiens.
These invertebrates included several caprellids, called skeleton shrimp
(Phylum Arthropoda, Class Crustacea, Order Amphipoda), a tiny nudibranch (above
right) Coryphella trilineata (Phylum Mollusca, Class Gastropoda,
Order Nudibranch), several acorn barnacles of the genus Lepas (Phylum
Arthropoda, Class Crustacea. Order Thoracica), and an unidentified worm
from the phylum Nemertea about 2mm long.